Problem: $ E = \left[\begin{array}{rrr}3 & -2 & -2 \\ 1 & -1 & -1 \\ 3 & -2 & 3\end{array}\right]$ What are the dimensions of matrix $ E$ ?
Explanation: The first dimension is the number of rows in the matrix. How many rows does $ E$ have? The second dimension is the number of columns in the matrix. How many columns does $ E$ have? So, $ E$ is a 3 $\times$ 3 matrix.